It is commonly known from the practice of plant protection that thiolcarbamates of the formula (I), particularly EPTC [S-ethyl-N,N-di(n-propyl)thiolcarbamate], butylate [S-ethyl-N,N-di(isobutyl)thiolcarbamate], vernolate [S-propyl-N,N-di(n-propyl)thiolcarbamate], ethiolate (S-ethyl-N,N-diethylthiolcarbamate), cycloate (S-ethyl-N-ethyl-N-cyclohexylthiolcarbamate) and molinate (S-ethyl-N,N-hexamethylenethiolcarbamate), as well as chloroacetanilides of the general formula (VIII), particularly alachlor (2-chloro-2',6'-diethyl-N-methoxymethylacetanilide), acetochlor (2-chloro-2'-ethyl-6'-methyl-N-ethoxymethylacetanilide) and propachlor (2-chloro-N-isopropylacetanilide) are very effective herbicides.
However, a common drawback of both classes of these herbicidally active agents consists in their relatively low selectivity against some cultivated plants, mainly maize.
When used in the usual herbicidally active doses, EPTC, vernolate and acetochlor may induce significant phytotoxic symptoms. About twenty five years ago, Hoffmann recognized that there are compounds, such as 1,8-naphthalic acid anhydride derivatives which are able to diminish the phytotoxic effect. Since that time, research has been undertaken to find synthetic compounds antagonizing the cultivated planting-damaging effect of herbicides.
The antidotal action of some compound classes have been disclosed in several Hungarian patent specifications mentioned hereinafter.
No. 165,736: The thiolcarbamate-antidoting action of dichloroacetamide derivatives, e.g. N,N-diallyl-2,2-dichloroacetamide (code No. R-25 788); PA0 No. 168,977: Oxazolidine and thiazolidine type antidotes, particularly useful against thiolcarbamates; PA0 No. 170,214: Thiazolidine sulfoxide and sulfone type antidotes, useful against thiolcarbamates and chloroacetanilides; PA0 No. 173,775: Sulfide type antidotes, useful against thiolcarbamates; PA0 No. 176,867: Oxazolidine derivatives useful for antidoting thiolcarbamates; PA0 No. 179,643: N-Benzoylsulfonylcarbamate compounds, useful for antidoting thiolcarbamates; PA0 No. 180,069: N-Benzoylsulfonylthiolcarbamate compounds, useful for antidoting thiolcarbamates; and PA0 No. 180,068: 2,3-Dibromopropionamide derivatives, useful as antidotes against thiolcarbamates; PA0 Nos. 174,487, 176,784, 180,422, 181,621, 183,997, 185,400 and 188,135: Substituted acetamide type antidotes, useful against thiolcarbamates and chloroacetanilides.
Dicarboxylic acid derivatives with different chemical structures antidoting thiolcarbamates and/or chloroacetanilides have been described in the Hungarian patent specifications Nos. 176,669, 176,796, 178,892 and 178,895; the antidoting effect of naphthalenecarboxylic acid derivatives has been described in the Hungarian patent specifications Nos. 178,883, 179,092 and 179,093.
A result in the increase of selectivity of thiolcarbamates has been described in a paper of J. E. Casida et al. "Thiocarbamate sulfoxide herbicides" in 1974. The main point of this paper is that the sulfoxide of EPTC, which is a decomposition product of EPTC, shows a useful herbicidal action but is not harmful to the maize. However, the recognition of these authors distended only to the use of the EPTC-sulfoxide in itself which cannot be used in practical plant protection because of its other disadvantageous properties (e.g. it cannot be used in all types of soils).
In spite of the results of research described in a large number of patent specifications, successful to find a compound that is able to provide general protection against the harmful effects of various herbicides, has not been found heretofore by the fact a fact supported also that the research directed to clarify the antidoting action were unable to develop a uniform standpoint for deciding the biochemical processes occurring in the case of adding antidotes, or for defining the influence of these antidotes on the processes induced by the herbicides in the cultivated plants.